Mercury is a highly toxic chemical element, also known as Quicksilver. Mercury enters your body through three ways: inhalation, skin contact, and ingestion. People nowadays ingest Mercury on nearly a daily basis. Fish such as shark, swordfish, tuna, and dolphin contain very high amounts of mercury.
How did these fish become contaminated? It happened through biomagnification. Biomagnification is the concentration of toxins in an organism from it ingesting other plants or animals where the toxins are more widely disbursed.
Biomagnification occurs like this: Mercury is released into the water or air through factory pollution ( such as coal burning and the mining of iron ) that enters the ocean through runoff and rain. Once in the ocean algae absorbs the Mercury, then the algae is eaten by tiny fish that now have more mercury than the algae. This is because say one algae has one amount of mercury, now the tiny fish has eaten twenty algae. Now the tiny fish is contaminated with twenty Mercury and a small fish eats twenty of the tiny fish. The small fish is now contaminated with four hundred Mercury. This continues until it reaches the apex predators sharks, swordfish, and dolphins (tuna are eaten by these predators so they also contain a very high amounts of Mercury). These Apex predators now are contaminated with an enormous amount of Mercury and when large amounts of these fish are consumed by humans we can contract Mercury poisoning. Mercury poisoning is deadly and symptoms include: Hearing impairment, tingling skin, difficulty speaking, lack of coordination, insanity, blindness, paralysis, coma, and death.
Might want to consider this next time you are eating a tuna sandwich.